BS EN 60255-27:2014

Measuring relays and protection equipment. Product safety requirements | Status: Current, Superseded

1 Scope This part of the IEC 60255 series describes the product safety requirements for measuring relays and protection equipment having a rated a.c. voltage up to 1 000 V with a rated frequency up to 65 Hz, or a rated d.c. voltage up to 1 500 V. Above these limits, IEC 60664‑1 is applicable for the determination of clearance, creepage distance and withstand test voltage. This standard details essential safety requirements to minimize the risk of fire and hazards caused by electric shock or injury to the user. This standard does not cover the safety requirements of installations. It does cover all the ways in which the equipment may be mounted and used in cubicles, racks and panels, and also retesting. This standard also applies to auxiliary devices such as shunts, series resistors, transformers, etc., that are used in conjunction with measuring relays and protection equipment and are tested together. Ancillary equipment used in conjunction with measuring relays and protection equipment may need to comply with additional safety requirements. This standard is intended to describe only product safety requirements; therefore, functional performance of the equipment is not covered. Functional safety requirements, including EMC functional safety, are not covered by this standard. Functional safety risk analysis is not within the scope of this product safety standard. This standard does not specify the implementation of individual equipment, circuits and components. The object of this standard is to have a comprehensive standard that covers all aspects of product safety and the related type and routine tests, for measuring relays and protection equipment. This standard applies to equipment designed to be safe at least under the following environmental conditions:

• – indoor use;
• – altitude up to 2 000 m, in accordance with IEC 60255‑1;
• – external operating temperature range, in accordance with IEC 60255‑1;
• – maximum external relative humidity 95 %, non-condensing, in accordance with IEC 60255‑1;
• – supply fluctuations in accordance with IEC 60255‑1;
• – applicable supply overvoltage category;
• – external pollution degree 1 and external pollution degree 2.

The equipment will normally be installed in a restricted access area within a power station, substation or industrial/retail environment. The environmental conditions specified for the equipment in IEC 60255‑1 apply. This standard considers the normal environmental conditions of corrosion caused by humidity but does not cover corrosion by atmospheric pollution. It is assumed that access to the equipment during installation, maintenance, normal service and decommissioning is restricted to users aware of working procedures necessary to ensure safety. This product safety standard takes precedence over general standards for matters of safety.